Accurately controlling the voltage output from a power supply does not simply entail the provision of an input voltage that will, based on the configuration of the power supply, generate the desired output voltage. For example, power supply circuitry should be controlled to generate a desired output voltage with minimal undershoot or overshoot caused by fast transient load changes. Output voltage undershoot or overshoot may be caused by, for example, a delay in response caused by characteristics of componentry in the circuitry of the power supply. For example, resistors, inductors, capacitors and other components having resistive, inductive or capacitive qualities take some finite time to reach the settling steady state because of their voltage/current storage characteristics. If this behavior is not accounted for, components may undercharge/overcharge as the power supply approaches steady state, causing the power supply output voltage to deviate significantly from the targeted value. Inaccuracy or deviation from the targeted value in the power supply output voltage can cause a malfunction or possibly even damage in a load being driven by the power supply, especially when the load includes sensitive circuitry (e.g., a microprocessor).
Higher accuracy in power supply output voltage may be realized through the use of one or more feedback loops. For example, the output voltage of a power supply may be fed back to control circuitry (e.g., via a feedback network) to more precisely control the power supply output voltage. Observer circuitry may also be employed as a secondary feedback loop to provide fast transient response (e.g., for loads that may include sensitive circuitry like a microprocessor). To realize fast transient response the observer circuitry may be very sensitive to changes in power supply output voltage, which makes the observer circuitry inappropriate for some power control schemes. For example, observer circuitry may not be appropriate for use with dynamic voltage scaling (DVS) that purposely changes the power supply output voltage in accordance with the DVS control scheme required by the load. The observer circuitry will try to prevent the desired voltage change, and as a result, the rate at which the power supply output voltage changes will be greatly reduced. Similar to output voltage inaccuracy, slow responsiveness in the power supply output voltage change may negatively affect performance for the load being driven, especially for sensitive loads.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications and variations thereof will be apparent to those skilled in the art.